Implementation of the FW CFG DMA interface.
When running a Linux guest on top of QEMU, using the -kernel option and with fw_cfg DMA Linux boot support, this is the timing improvement for x86:
Original QEMU and SeaBIOS QEMU startup time: .080 BIOS startup time: .060 Kernel setup time: .586 Total time: .726
QEMU and SeaBIOS with this patch series and fw_cfg DMA Linux boot support QEMU startup time: .080 BIOS startup time: .039 Kernel setup time: .005 Total time: .126
QEMU startup time is the time between the start and the first kvm_entry. BIOS startup time is the time between the first kvm_entry and the start of function do_boot, in SeaBIOS. Kernel setup time is the time between the start of the function do_boot in SeaBIOS and the jump to the Linux kernel.
As you can see, both the BIOS (because of ACPI tables and other configurations) and the Linux kernel boot (because of the copy to memory) are greatly improved with this new interface.
Also, this new interface is an addon to the old interface. Both interfaces are compatible and interchangeable.
Changes from v1: - Take into account order of fields in the FWCfgDmaAccess structure - Check and change endianness of FWCfgDmaAccess fields - Change order of fields in the FWCfgDmaAccess structure - Add FW_CFG_DMA_CTL_SKIP feature for control field - Split FW_CFG_SIZE in QEMU - Make FW_CFG_ID a bitmap of features - Add 64 bit address support for the transfer. Trigger when writing the low address, and address is 0 by default and at the end of each transfer. - Align ports and addresses. - Preserve old fw_cfg_comb_valid behaviour in QEMU - Update documentation to reflect all these changes
Changes from v2: - Make IOports fw_cfg DMA region a different IO region. - Reuse everything for MMIO and IOport DMA regions - Make transfer status only based on control field - Use DMA helpers instead of direct map/unmap - Change ARM fw_cfg DMA address space - Change Linux boot process to match linuxboot.S - Add select capabilities in the FWCfgDmaAccess struct - Update documentation to reflect all these changes
Changes from v3: - Set properly fw_cfg DMA fields in ARM - Set fw_cfg DMA boot process properly (by Laszlo Ersek) - Add signature to fw_cfg DMA address field (by Kevin O'Connor) - Minor nitpicks
Changes from v4: - Remove Linux fw_cfg boot from this series (will be sent separately) - Minor nitpicks
Add support for the new fw_cfg DMA interface. The protocol is explained in QEMU documentation.
Signed-off-by: Marc Marí markmb@redhat.com --- src/fw/paravirt.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++------ src/fw/paravirt.h | 26 +++++++++++++++--- 2 files changed, 93 insertions(+), 12 deletions(-)
diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c index db22ae8..65f9fba 100644 --- a/src/fw/paravirt.c +++ b/src/fw/paravirt.c @@ -23,6 +23,7 @@ #include "util.h" // pci_setup #include "x86.h" // cpuid #include "xen.h" // xen_biostable_setup +#include "stacks.h" // yield
// Amount of continuous ram under 4Gig u32 RamSize; @@ -30,6 +31,13 @@ u32 RamSize; u64 RamSizeOver4G; // Type of emulator platform. int PlatformRunningOn VARFSEG; +// cfg_dma enabled +int cfg_dma_enabled = 0; + +inline int qemu_cfg_dma_enabled(void) +{ + return cfg_dma_enabled; +}
/* This CPUID returns the signature 'KVMKVMKVM' in ebx, ecx, and edx. It * should be used to determine that a VM is running under KVM. @@ -199,23 +207,63 @@ qemu_cfg_select(u16 f) }
static void +qemu_cfg_dma_transfer(void *address, u32 length, u32 control) +{ + QemuCfgDmaAccess access; + + access.address = cpu_to_be64((u64)(u32)address); + access.length = cpu_to_be32(length); + access.control = cpu_to_be32(control); + + barrier(); + + outl(cpu_to_be32((u32)&access), PORT_QEMU_CFG_DMA_ADDR_LOW); + + while(be32_to_cpu(access.control) & ~QEMU_CFG_DMA_CTL_ERROR) { + yield(); + } +} + +static void qemu_cfg_read(void *buf, int len) { - insb(PORT_QEMU_CFG_DATA, buf, len); + if (len == 0) { + return; + } + + if (qemu_cfg_dma_enabled()) { + qemu_cfg_dma_transfer(buf, len, QEMU_CFG_DMA_CTL_READ); + } else { + insb(PORT_QEMU_CFG_DATA, buf, len); + } }
static void qemu_cfg_skip(int len) { - while (len--) - inb(PORT_QEMU_CFG_DATA); + if (len == 0) { + return; + } + + if (qemu_cfg_dma_enabled()) { + qemu_cfg_dma_transfer(0, len, QEMU_CFG_DMA_CTL_SKIP); + } else { + while (len--) + inb(PORT_QEMU_CFG_DATA); + } }
static void qemu_cfg_read_entry(void *buf, int e, int len) { - qemu_cfg_select(e); - qemu_cfg_read(buf, len); + if (qemu_cfg_dma_enabled()) { + u32 control = (e << 16) | QEMU_CFG_DMA_CTL_SELECT + | QEMU_CFG_DMA_CTL_READ; + qemu_cfg_dma_transfer(buf, len, control); + } else { + qemu_cfg_select(e); + qemu_cfg_read(buf, len); + } }
struct qemu_romfile_s { @@ -230,9 +278,14 @@ qemu_cfg_read_file(struct romfile_s *file, void *dst, u32 maxlen) return -1; struct qemu_romfile_s *qfile; qfile = container_of(file, struct qemu_romfile_s, file); - qemu_cfg_select(qfile->select); - qemu_cfg_skip(qfile->skip); - qemu_cfg_read(dst, file->size); + if (qfile->skip == 0) { + /* Do it in one transfer */ + qemu_cfg_read_entry(dst, qfile->select, file->size); + } else { + qemu_cfg_select(qfile->select); + qemu_cfg_skip(qfile->skip); + qemu_cfg_read(dst, file->size); + } return file->size; }
@@ -422,8 +475,18 @@ void qemu_cfg_init(void) for (i = 0; i < 4; i++) if (inb(PORT_QEMU_CFG_DATA) != sig[i]) return; + dprintf(1, "Found QEMU fw_cfg\n");
+ // Detect DMA interface. + u32 id; + qemu_cfg_read_entry(&id, QEMU_CFG_ID, sizeof(id)); + + if (id & QEMU_CFG_VERSION_DMA) { + dprintf(1, "QEMU fw_cfg DMA interface supported\n"); + cfg_dma_enabled = 1; + } + // Populate romfiles for legacy fw_cfg entries qemu_cfg_legacy();
diff --git a/src/fw/paravirt.h b/src/fw/paravirt.h index 95ffb92..ed8e5f1 100644 --- a/src/fw/paravirt.h +++ b/src/fw/paravirt.h @@ -9,6 +9,12 @@ #define PF_XEN (1<<1) #define PF_KVM (1<<2)
+typedef struct QemuCfgDmaAccess { + u32 control; + u32 length; + u64 address; +} PACKED QemuCfgDmaAccess; + extern u32 RamSize; extern u64 RamSizeOver4G; extern int PlatformRunningOn; @@ -25,11 +31,23 @@ static inline int runningOnKVM(void) { }
// Common paravirt ports. -#define PORT_SMI_CMD 0x00b2 -#define PORT_SMI_STATUS 0x00b3 -#define PORT_QEMU_CFG_CTL 0x0510 -#define PORT_QEMU_CFG_DATA 0x0511 +#define PORT_SMI_CMD 0x00b2 +#define PORT_SMI_STATUS 0x00b3 +#define PORT_QEMU_CFG_CTL 0x0510 +#define PORT_QEMU_CFG_DATA 0x0511 +#define PORT_QEMU_CFG_DMA_ADDR_HIGH 0x0514 +#define PORT_QEMU_CFG_DMA_ADDR_LOW 0x0518 + +// QEMU_CFG_DMA_CONTROL bits +#define QEMU_CFG_DMA_CTL_ERROR 0x01 +#define QEMU_CFG_DMA_CTL_READ 0x02 +#define QEMU_CFG_DMA_CTL_SKIP 0x04 +#define QEMU_CFG_DMA_CTL_SELECT 0x08 + +// QEMU_CFG_DMA ID bit +#define QEMU_CFG_VERSION_DMA 2
+int qemu_cfg_dma_enabled(void); void qemu_preinit(void); void qemu_platform_setup(void); void qemu_cfg_init(void);
On Thu, Oct 08, 2015 at 05:03:26PM +0200, Marc Marí wrote:
Add support for the new fw_cfg DMA interface. The protocol is explained in QEMU documentation.
Thanks - I committed this patch.
-Kevin
-
Kevin O'Connor -
Marc Marí